About CryptoKitties: I assume it's composing scalable vector graphics (SVG), see Hacking the CryptoKitties Genome for an article and reverse-engineered remake from 2017 - that's the best (and only?) open source version I found.
Opening up the SVGs it was easy to see the different parts of the kitty... Isolating the SVG elements for each of these genes allowed me build a quick React.js prototype that was able to render a kitty of any possible phenotype.
The (build in public) next-gen CryptoKitties 2.0 (demo) designer / renderer for the flow (blockchain meowgration) is starting up unity in the browser - as far as I can remember, see CryptoKitties v2.0 - From Ethereum to Flow (Blockchain) - Build In Public to try it yourself.
More insights or points to articles, open source projects and more welcome.
PS: About Cryptopunks: Cryptopunks works different, that is, with composing 24x24 pixel images on top of each other I assume, see Inside the Punk Art Machinery - How To Generate 10 000 Punks (and Punkettes), Algorithmically - Paint by Numbers for a (reverse-engineered) open source remake (incl. the pixel images for composing punks).